Lakes Are Sentinels of Climate Change

Across the vast landscape of the Earth, where are scientists likely to find the clearest signals of climate change so that they can predict future impact? According to Craig Williamson, Miami University professor of zoology and Ohio Eminent Scholar of Ecosystem Ecology, lakes and reservoirs are an important part of the answer.

Williamson and colleagues Jasmine Saros, University of Maine, Orono, and David Schindler, University of Alberta, Edmonton, provide highlights of recent research on lakes in “Sentinels of Change” a Perspectives article published in the Feb. 13 issue of Science magazine.

“Research on lakes in three different areas has really come together to show how important lakes are, in not only acting as sentinels to provide information on how climate change influences freshwater resources, but also acting as integrators by storing the signals of past climate change in their sediments,” Williamson said.

“In addition, it turns out lakes are real ‘hot spots’ of climate regulation,” Williamson continued. “For example, while lakes make up only about three percent of the surface area of the terrestrial landscape, they bury about four times as much carbon as the world’s oceans.”

Williamson and Saros were the lead organizers of an international American Geophysical Union Chapman Conference at Lake Tahoe in September 2008. Scientists and students from 18 countries examined the role of lakes and reservoirs as sentinels, integrators and regulators of climate change and discussed how to incorporate inland waters into global climate models.

Scientists at the conference noted that past modeling efforts have ignored the role of smaller lakes in global climate models. More than 90 percent of the estimated 304 million lakes worldwide are small (less than 0.01 km2) and shallow. “Including lakes and reservoirs in global climate models may shift estimates for many landscapes to greater sources of carbon dioxide,” Williamson said.

Given that freshwater is one of Earth’s resources most jeopardized by changing climate, being able to detect changes that are detrimental to water quality is critically important, according to the researchers. Sentinels of change include decreases in water levels in many lakes, decreases in the duration of winter ice cover by 12 days in the past 100 years, fish kills and changes in plankton communities.

“The outlook for lakes and reservoirs and the ecosystem services they provide is bleak,” state the researchers. “Yet records from these inland waters may provide the insights necessary to address the dual challenges of climate change and increased human domination and their effects on lakes and the larger landscape.”

Global lake observatory networks that monitor and integrate these signals are needed in combination with experimental studies, in order to decipher all the information contained in the waters and sediments of lakes, suggest the scientists.

The proceedings of the “Sentinels of Change” conference will be published as a special issue of the journal Limnology and Oceanography.

Williamson’s research on lakes includes work on alpine and subalpine lakes in the Beartooth Mountains of Montana and Wyoming, the Canadian Rocky Mountains and Lake Tahoe in California, as well as lower elevation lakes in Pennsylvania and reservoirs in Ohio.

“One of the more notable studies that we have just begun is of some of the high lakes in the Andes on the border of Chile and Bolivia. We are working with NASA scientists in an attempt to understand life in extreme environments with some of the highest levels of UV radiation that have been observed on Earth, and in a region where climate change is proceeding at a rate that threatens lakes with drying up,” Williamson explains. “Another particularly interesting study is examining the role of changes in the UV transparency of the waters of Lake Tahoe and how this is allowing warmwater fish species to invade and spread in the lake.”

Craig Williamson may be contacted at 513-529-3180; Skype: craig.e.williamson in Oxford, United States; craig.williamson@muohio.edu; http://www.users.muohio.edu/willia85/.